1. Field of the Invention
The present invention relates to a thermal activation device for thermally activating a heat-sensitive adhesive layer of a sheet material having a printing layer formed on one surface of a sheet-like base material and the heat-sensitive adhesive layer formed on the other surface thereof. The present invention also relates to a method of conveying the sheet material.
2. Description of the Related Art
For example, in distribution centers and shops, labels for displaying various types of information such as prices and for displaying barcodes for management by means of POS (point of sales) terminals have been used by being attached to articles. As this type of label, a proposal has been made of a label, which is issued using a sheet material having a printing layer formed on one surface of a sheet-like base material and a heat-sensitive adhesive layer formed on the other surface thereof.
In general, a label issuing instrument which issues the label having the heat-sensitive adhesive layer as described above includes a sheet supply apparatus that supplies the sheet material, a printing apparatus that prints various types of information on a thermal printing layer of the sheet material supplied from the sheet supply apparatus, a cutting apparatus that cuts the sheet material for which the printing has been performed by the printing apparatus, and a thermal activation device that thermally activates the heat-sensitive adhesive layer of the sheet material.
Moreover, as a conventional label issuing instrument including the thermal activation device, there is known a structure in which a guiding apparatus that sags and guides the sheet material is disposed between the cutting apparatus and the thermal activation device (for example, refer to. JP 2003-316265 A).
Incidentally the label issued from the sheet material having the heat-sensitive adhesive layer is sometimes used in such a manner that the entire surface of the heat-sensitive adhesive layer is not thermally activated evenly, but only a part thereof is thermally activated to form an adhesive region, and the other portions are left as a non-adhesive region which is not thermally activated.
In such a label, for example, one end side as the adhesive region of the label is attached to an article and the other end side as the non-adhesive region is not attached to the article. Moreover, in the label, for example, a tear-off line or the like is provided on a border between the adhesive region and the non-adhesive region, and in a distribution process of such articles, the other end side of the label is cut off and used as a slip for management.
As described above, in the conventional thermal activation device, when the heat-sensitive adhesive layer of the sheet material is thermally activated partially in the width direction perpendicular to the conveying direction of the sheet material, the adhesive region thermally activated by a thermal activation head and the non-adhesive region which is not thermally activated are unevenly present in the width direction of the sheet material.
As shown in FIG. 8, in a conventional thermal activation device 110, a heat-sensitive adhesive layer of a sheet material 103 held between a thermal activation head 111 and a platen roller 112 is thermally activated partially at a thermal activation position P2 of the thermal activation head 111.
For example, with respect to a centerline C in a direction of a width W1 perpendicular to the conveying direction of the sheet material 103 as a direction indicated by an arrow L, a region with a width W2 from the centerline C to one end side is formed into an adhesive region 121, and a region with a width W2 from the centerline C to the other end side is formed into a non-adhesive region 122. In this case, with respect to the centerline C of the sheet material 103 in the direction of the width W1, a friction coefficient differs between the adhesive region 121 and the non-adhesive region 122.
Therefore, there is a problem in that, in the sheet material 103, the conveying speed of the adhesive region 121 becomes v1, the conveying speed of the non-adhesive region 122 becomes v2, and the conveying speed v1 of the adhesive region 121 becomes larger than the conveying speed v2 of the non-adhesive region 122, the conveying of the sheet material 103 being performed by the platen roller 112 which is brought into press contact with the sheet material 103.
As a result, a difference occurs between the respective conveying speeds v1 and v2 in the width direction by the platen roller 112, and thus there is a problem in that the sheet material 103 is inclined with respect to the conveying direction to cause skew feed.
Hence, in the conventional thermal activation device, the sheet material is inclined as described above, and thus the respective widths W2 of the adhesive region 121 thermally activated by the thermal activation head 111 and the non-adhesive region 122 which is not thermally activated are changed. Accordingly, it has been difficult to form the adhesive region having an intended width on the heat-sensitive adhesive layer of the sheet material 103.